Synthesis of ZnGa2O4 assisted by high-energy ball milling and its gas-sensing characteristics

• Synthesis of ZnGa2O4 via a simple solid state reaction assisted by high-energy ball-milling.
• Highly gas sensing property of ZnGa2O4 to detect LPG and NO2 at different operating temperatures.
• Promising sensing responses and the possibility of discriminating between reducing and oxidizing species.

Mass production of ZnGa2O4 has been successfully achieved via a simple solid state reaction assisted by high-energy ball-milling of mixtures of ZnO and GaOOH powder at room temperature. The samples were characterized in detail to confirm the formation of ZnGa2O4. It could be concluded from the result of X-ray diffraction patterns that the crystal formation started after milling for 5 h, and it was completed after 7 h. The average diameter of the as-prepared ZnGa2O4 is less than 100 nm. To demonstrate the potential applications, we have fabricated a gas sensor based on the as-synthesized ZnGa2O4 and investigated it for liquid petroleum gas (LPG) and nitrogen dioxide gas (NO2) detection at different working temperatures. ZnGa2O4 sensors exhibited a gas response (Ra/Rg = 7.9, Ra: resistance in air, Rg: resistance in gas) to 50 ppm of LPG at working temperature 340 °C, and a superior gas response (Rg/Ra = 16.2) to 5 ppm of NO2 at 240 °C. Preliminary functional tests indicated promising sensing responses and the possibility of discriminating between reducing and oxidizing species as a function of the working temperature.

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